ALLOWANCE FOR DOUBTFUL ACCOUNTS RECEIVABLES

We evaluate the collectibility of accounts receivable based on a combination of factors. We estimate an allowance for doubtful accounts as a percentage of net sales based on historical bad debt experience. This estimate is periodically adjusted when we become aware of a specific customer’s inability to meet its financial obligations (e.g., bankruptcy filing) or as a result of changes in the overall aging of accounts receivable. While we have a large number of customers that operate in diverse businesses and are geographically dispersed, a general economic downturn in any of the industry segments in which we operate could result in higher than expected defaults, and, therefore, the need to revise estimates for the provision for doubtful accounts could occur.

Allowance for doubtful accounts receivable consisted of the following:



	June 30,
	2015			2014
	($ in millions)
Balance at beginning of year	$	3.0		$	3.4
Provisions (credited) charged	(0.2		)	0.7
Write-offs, net of recoveries	(0.1		)	—
Balance at end of period	$	2.7		$	4.1

Provisions (credited) charged to operations were $(0.4) million and $0.4 million for the three months ended June 30, 2015 and 2014, respectively.